A semiconductor device comprising enhancement and depletion mode insulated gate field effect transistors is described in a paper entitled `Smart-SIPMOS- an intelligent power switch` by M. Glogolja and Dr. J. Tihanyi, published in the Conference Record of the 1986 IEEE Industry Applications Society Annual Meeting Part 1 at pages 429 to 433. As indicated in the title of the aforementioned paper, the semiconductor device described is an intelligent power switch, that is a semiconductor device in which one or more power semiconductor components are provided in or on the same semiconductor body as logic components for controlling and monitoring operation of the power semiconductor component and a load in circuit with the switch.
Such an intelligent power switch may, for example, be used as a high side switch in automotive and industrial control applications to control lights, electric motors, etc. Thus, for example, in combination with a simple bus system and central control unit such intelligent power switches may be used to replace the wiring loom of a motor vehicle. In such a situation the power supply to the intelligent power switch will be provided by the vehicle's battery.
The intelligent power switch described in the aforementioned paper comprises a vertical power MOSFET which forms the power switch and CMOS circuitry for controlling the operation of the power switch and for providing fault detection, for example detection of overvoltage or overtemperature problems. The CMOS circuitry includes low voltage complementary lateral IGFETs, high voltage P and N-channel enhancement IGFETs and high voltage depletion mode IGFETs.